This invention relates to a composite wood product, hereinafter referred to as “The Product”, and its method of manufacture. More particularly, the composite wood product is manufactured from oriented strands of wood.
Engineered lumber products are well known and are used in the following structural applications:                1. Beams, headers, and/or columns        2. Joists        3. Rafters        4. Studs        5. Components in complex products targeted at one of the prior segments, for example, as a tension chord in a plated roof truss.        
A composite wood product is one that is composed of wood and glue. All composite wood products are engineered wood products. Not all engineered wood products are composite wood products. Roof trusses, floor trusses, wood I-joists and box beams are complex components, that is, engineered wood products but are not necessarily composite wood products. When producing a composite wood product, a log cut from a tree is broken down into smaller elements and then reformed into a new product that has the elements glued together with resin. There are two major types of composite wood products. The first type are board products which include plywood, particleboard, oriented strand board (or its predecessor wafer board) and medium density fiber board. Only plywood and oriented strand board are widely used in the construction of buildings. They are used for the sub strata in roofing, siding and flooring. Plywood is made from veneer sheets about 54 inches (1.4 m) by 102 inches (2.6 m). Oriented strand board is made from wafers most of which are less than 6 inches (15 cm) long, less than two inches (5 cm) wide and less than 1/25 inch (1 mm) thick. One other product that is unique among board type products is Timberstrand™ long strand lumber (LSL). It is essentially waferboard bonded together in a steam injection press by an isocyanate resin. The wafers it uses are up to 12 inches (30 cm) long rather than the OSB maximum of about 6 inches (15 cm). This product was developed for use in industrial applications such as for core stock in cabinetry, doors and windows. It has been used in structural applications such as short span low strength headers, rim joist in competition with OSB, and very occasionally as 2 by 6 studs.
The second type of composite wood products are structural lumber products which are used to build the frame of a structure, essentially the supporting skeleton. The four principal uses for structural lumber products are as beams (and headers), joists, rafters and studs. The main composite lumber products are glue laminated timber (glulam), laminated veneer lumber (LVL), and parallel strand lumber (PSL). Glulam is made by gluing common dry lumber together to form larger beams. LVL is essentially plywood but with all of the veneer sheets having the grain direction parallel. The maximum width of a billet of LVL is about 48 inches (122 cm) after trimming because that is the width produced by the current technology for producing veneer.
Parallel strand lumber (PSL), known commercially as Parallam™ is the only composite lumber product utilizing long veneer strands (up to 102 inches (2.6 m)) with some similarities to those of “The Product” of this patent application. PSL was patented by Barnes as described in U.S. Pat. No. RE. 30,636. Both PSL and the product of the present invention consist of veneer strands bound together by phenol formaldehyde resin, however, they have a different internal structure and are manufactured according to different processes and are targeted at different market segments. These factors have resulted in products with quite different properties.
The differences between the PSL product and the product of the present invention can be summarized as follows:    1. The billet dimensions are very different and can not be the same. “The Product” is preferably made in billets over 3 feet (91 cm) wide whereas the PSL billet has never been made over 2 feet (61 cm) wide. The PSL billet is about 12 inches (30 cm) deep. The limit on the width of PSL is due to utilizing microwave pressing. The microwaves are introduced into the press through microwave transparent windows and penetration depth limits the width of billet that can be manufactured. By comparison, “The Product” billet can be made in widths over 12 feet (3.7 m), the limit being the width of commercially available presses. However, the thickness of “The Product” billet can not practically exceed 2 inches (5 cm) because hot pressing a mat thicker than that would thermally damage the outer layers of “The Product” before the core could be brought to a temperature over the 212 degrees Fahrenheit (100° C.) needed for curing the resin.    2. The utilization of materials for out door applications is different. PSL has a wax component added so that the material can better resist moisture uptake and can be used in out door applications. “The Product” is targeted for indoor buried applications and does not require a wax content.    3. The minimum length strands differs. PSL does not utilize strands under two feet in length for two reasons. The beam and header application to which it is targeted requires relatively high strength, which cannot be met if the strands shorter than two feet are included. Also the resin application system will not work well with short strands. “The Product” can utilize short strands for the lower strength market targets of joists and rafters. Also, “The Product” resin application system is not hindered by short strands.    4. Visually the sides of the two products are different. PSL beams and headers are sawn on all four sides from the billet. This sawing results in the product having substantially the appearance of wood. “The Product” joists and rafters are gang sawed from the billet. This results in the wide face of the product having a dark colored appearance (of a resin coating) with only the small face, or top and bottom, having the appearance of wood. Fewer sawing cuts results in a higher product yield for “The Product” than the yield for PSL.    5. “The Product” may be made from different thickness veneer strips in a random or layered pattern. Such mixing of veneers of differing thickness allows for “The Product” to be more cost competitive in that less expensive veneers can be mixed with more costly veneers.    6. “The Product” may be made from mixed different species of logs with the resultant strands either being mixed or layered. Such species mixing allows “The Product” to be more cost competitive in that a wide variety of timber or logs can be used.    7. Product layering potential is different. “The Product” may layer its product by species, thickness or other wood characteristics, whereas the PSL process mixes all wood entering the process and layering is not possible in the commercial facilities. Such layering may have either aesthetic or structural benefits (e.g. having a more dense core for higher fastener holding characteristics.    8. There is a difference in production cost potential. “The Product” strength requirement in the joist and rafter segment is less than the strength requirement in the beam and header segment served by PSL. This lower strength requirement for “The Product” allows it to utilize a lower grade and lower cost veneer. The ability to utilize shorter strands with resulting lower trim and saw losses results in a significantly higher utilization and therefore lower cost than for PSL. In summary, “The Product” is better positioned to compete in the joist and rafter segments. PSL has better, although more costly, attributes to compete in the beam and header segment. Physically the products and processes are different and each will not compete substantially against the other in the others selected market segments.
Market research studies have shown that the market would utilize a solid rectangular engineered wood product as a joist and rafter if it had adequate strength and have a price competitive with those of wood I joists and wide dimension kiln dried lumber. To be a direct substitute for those two current products it would need to have a modulus of elasticity of at least 1.5 million p.s.i (10 million kPa). Attempts at waferized lumber, OSB and LSL, have not obtained adequate strength properties to compete successfully in the joist and rafter segments. The only significant structural composite lumber products (PSL, LVL, and Glulam) that would make an excellent joist are too costly to produce and sell as rafters and joists. Therefore, they are limited mainly to use in the higher priced but smaller beam and header market segment. “The Product” of the present invention is targeted principally for use as a joist and rafter, although it has some potential for use as a stud, beam or as a component in roof trusses.
Most wood based joists used in single and low rise multiple construction include conventional lumber, parallel chord plated trusses, and I-joists. With the decline of the quality of forests being harvested for wood products, the quality of wide dimension lumber used as joists is also declining in quality and as a percent of total lumber manufactured. This decline in quality has allowed for market penetration by wood I-joists and parallel chord plated trusses. Few companies publish their sales by product volumes so only rough estimates of market share are available but the I-joist share is estimated to be over 20% and the truss share to be over 15%. Both products are usually priced higher per lineal foot than conventional lumber. Their manufacturers market them by extolling attributes that they claim are superior to those of conventional lumber.
Among the benefits of “The Product” of the present invention are superior strength, uniformity, long lengths, and fire resistance. These attributes result in a safer building material than the others utilized as joists.
The key benefit of the product of the present invention is that it can be manufactured for a lower cost than the other two engineered lumber joist products (plated trusses and wood I-joists) and in most cases at a lower cost than conventional kiln dried wide dimension lumber. There are four main cost components in producing an engineered lumber product:    1. Wood—The major savings that can be obtained by composite wood products are in this area. Higher yields (volume of product output divided by volume of green logs entering the process) may be realized. Also, with some composite products, a lower grade log (with lower costs) may be utilized.    2. Labor—Increased capital investment may eliminate some labor, however the overall manufacturing process used is a strong factor. The simpler the process flow, the more easily it is automated. If a product can be sold by having the lowest price, substantial marketing and technical service activities can be minimized.    3. Energy—The energy required to break down the log, dry the furnish, heat and cure the resin, and heat and illuminate a plant is similar in most wood product plants. Savings potential associated with energy use is therefore limited.    4. Resin—Most composite structural lumber products use phenol formaldehyde resin because it is the lowest cost resin that has adequate bonding strength, it is waterproof when cured, and it is highly resistant to ultra violet light degradation. It also has fewer environmental problems than alternative resins.
“The Product” has lower costs of manufacture than its potential competitors. This is mainly because the product of the present invention enjoys a much higher yield of final product from the log than do any of its potential competitors. Logs with an average base diameter of 13 inches (33 cm) will yield about 65% of this product in volume whereas I-joist, plated trusses, or conventional lumber processes will have yields of less than 40%. This 63% [(65/40)−1] higher yield not only results in potential cost savings to the construction industry but will tend to result in 38% [1−(40/65)] fewer trees being harvested, which has many attendant and obvious environmental benefits. The product of the present invention provides little, if any, reduction in resin costs. The simpler plant flows will have some cost savings on energy usage and some savings on plant labor. The major labor savings will be in under pricing the competition and being able to provide lower levels of promotion and technical sales support.